Meng Yuecheng, Lou Li, Shao Zhipeng, Chen Jie, Li Yanhua, Zhang Tianqi
School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou 310018, China.
Research and Development Center, Wuxi Biortus Biosciences Co., Ltd., Jiangyin 214437, China.
Foods. 2022 Aug 2;11(15):2311. doi: 10.3390/foods11152311.
ε-Polylysine (ε-PL) is a cationic antimicrobial peptide, which easily forms complexes with food polyanions to weaken its antibacterial activity. A whey protein-ε-PL complex delivery system was found to be able to solve this problem. This study investigated the antimicrobial activity of the complexes and their mechanism against Gram-positive bacteria. The minimal inhibitory concentration of the complexes with different ε-PL contents against and were 19.53-31.26 and 3.90-7.81 μg/mL, respectively, which were similar to free ε-PL. Furthermore, the whey protein-ε-PL complexes had a strong bactericidal effect on . The inhibition zone diameters of the complexes against and containing 5000 μg/mL of ε-PL were 14.14 and 16.69 mm, respectively. The results of scanning electron microscopy showed that the complexes could destroy the cell membrane structure in , resulting in holes on the surface, but not in . The results of molecular dynamics simulation showed that under electrostatic interaction, the complexes captured the phospholipid molecules of the bacterial membrane through the hydrogen bonds. Parts of the ε-PL molecules of the complexes were embedded in the bilayer membrane, and parts of the ε-PL molecules could penetrate the bilayer membrane and enter the bacterial internal environment, forming holes on the surface of the bacteria. The antibacterial results in fresh meat showed that the whey protein-ε-PL complexes could reduce the total mesophilic and counts. This study on the antibacterial activity mechanism of whey protein-ε-PL complexes could provide a reference for the application of ε-PL in protein food matrices.
ε-聚赖氨酸（ε-PL）是一种阳离子抗菌肽，它很容易与食品中的多阴离子形成复合物，从而削弱其抗菌活性。研究发现，乳清蛋白-ε-PL复合递送系统能够解决这一问题。本研究考察了该复合物对革兰氏阳性菌的抗菌活性及其作用机制。不同ε-PL含量的复合物对金黄色葡萄球菌和单核细胞增生李斯特菌的最低抑菌浓度分别为19.53 - 31.26 μg/mL和3.90 - 7.81 μg/mL，与游离ε-PL相似。此外，乳清蛋白-ε-PL复合物对金黄色葡萄球菌有很强的杀菌作用。含5000 μg/mL ε-PL的复合物对金黄色葡萄球菌和单核细胞增生李斯特菌的抑菌圈直径分别为14.14 mm和16.69 mm。扫描电子显微镜结果表明，该复合物可破坏金黄色葡萄球菌的细胞膜结构，导致其表面出现孔洞，但对单核细胞增生李斯特菌无此作用。分子动力学模拟结果表明，在静电作用下，复合物通过氢键捕获细菌膜的磷脂分子。复合物中部分ε-PL分子嵌入双层膜，部分ε-PL分子可穿透双层膜进入细菌内部环境，在细菌表面形成孔洞。鲜肉中的抗菌结果表明，乳清蛋白-ε-PL复合物可降低嗜温菌总数和单核细胞增生李斯特菌数量。本研究对乳清蛋白-ε-PL复合物抗菌活性机制的研究可为ε-PL在蛋白质食品基质中的应用提供参考。
